The synchronous buck converter circuit is commonly used for DC/DC switching applications. Traditionally, the silicon based MOSFET is used in these circuits. III-nitride based heterojunction switches are also well known and have greater current capacity and improved voltage withstand ability than a silicon based device of the same size and have reduced parasitic capacitances. However, many III-nitride based switches suitable for power applications are normally on in the absence of a gate signal.
A circuit according to the present invention is a converter that includes a first switch, a III-nitride depletion mode switch, and an enhancement mode switch disposed in the path of conduction to the III-nitride depletion mode switch to selectively open/close the conduction path to the III-nitride depletion mode switch.
According to one aspect of the present invention, the enhancement mode switch enables the conduction of current to the III-nitride switch.
According to another aspect of the present invention, the enhancement mode switch cuts off the current to the III-nitride switch.